1. Field of the Invention
The present invention concerns an arrangement for a discharge system for combustion gases and heated cooling air from an internal combustion engine-driven vehicle, in which the cooling-air and exhaust-gas discharge system has a gas outflow channel which opens in an open aperture in the vehicle""s bodywork. The invention is specifically intended for application to military motor vehicles, such as tracked vehicles, tanks and similar, to give the vehicle""s exhaust discharge system a low thermal signature, so-called IR signature, in order to protect against detection of the vehicle by heat-seeking cameras.
2. Description of Related Art
As disclosed in DE-A-3 221 378, the hot combustion gases from the engine in a known military vehicle are mixed with cooling air in a collecting chamber in the lower part of the vehicle before being released through a plurality of grated openings in the underside of the vehicle""s bodywork. However, with a gas discharge arrangement of this kind, an increased IR signature is obtained since the exhaust gases warm up the underlying ground as well as the underside of the bodywork through contact with the gases.
U.S. Pat. No. 4,864,819 describes an exhaust gas outlet from a gas turbine-driven military vehicle where the outlet is provided with strong, inclined ballistic engine protection plates which can be cooled internally and externally with cooling air flowing through a small number of slots at, between or in these plates in order to reduce their temperature as sensed from the outside. No means for effective cooling of those parts of the outlet located directly adjacent to the aperture are disclosed; instead the exhaust gases can by turbulence mix with the peripheral cooling air and heat up the outlet aperture, and thus the vehicle is not given an optimally low IR signature.
U.S. Pat. Nos. 3,981,448, 3,921,906 and GB-1 128 532 disclose other arrangements to deflect the exhaust gases from jet engines and simultaneously to cool the deflecting surfaces down by bringing in external cooling air.
According to the present invention, a cooling arrangement is disclosed for an internal combustion engine-driven land vehicle, where not only the vehicle""s engine but other heat-emitting sources and its exhaust outlet can be cooled effectively by means of a common fan unit and thereby improve the vehicle""s IR signature, irrespective of whether the vehicle is moving or stationary.
For this objective the arrangement according to the invention as mentioned by way of introduction comprises a motor radiator mounted in the gas outflow channel; a silencer connected to the vehicle""s internal combustion engine and opening into the gas outflow channel downstream of the motor radiator in such a way that the silencer outlet is not directly visible from outside through the gas outflow channel""s discharge aperture, said gas outflow channel having, at least in an area of the same adjacent to the aperture, a boundary wall which is perforated right up to the open aperture and surrounded by a cooling air channel; and a motor-driven fan placed in a space upstream of the motor radiator for the purpose of generating forced cooling air streams partly through the radiator and partly through the cooling air channel via bypass openings, so that cooling air in the cooling air channel can sweep over the inner side as well as the outer side of the perforated wall in order to cool it and prevent direct contact between the exhaust gases and the perforated wall.
Additional characteristics of the arrangement according to the present invention are disclosed in closer detail below by reference to the appended drawing.